In typical pressure regulators for automotive fuel systems, there is often provided a pressure regulator having a movable wall or diaphragm dividing the regulator into chambers on opposite sides thereof at different pressures. The difference in pressure determines the position of the diaphragm, which in turn determines the size of a flow passage through the regulator. Thus, depending upon the difference in pressure on opposite sides of the diaphragm, the flow through the regulator is regulated to a predetermined pressure. In returnless fuel systems, for example, as illustrated in U.S. Pat. No. 5,413,077 of common assignee herewith, the disclosure of which is incorporated herein by reference, the diaphragm controls the position of a ball valve which is spring-biased toward a valve seat. Fuel flows past the spring and normally opened ball valve into a compartment on one side of the diaphragm for flow to a fuel rail. The opposite side of the diaphragm may have a vacuum reference. It will be appreciated that the difference in pressure between the chambers on the opposite sides of the diaphragm displaces the diaphragm, which in turn mounts a post for moving the ball valve away from the seat or permitting the ball valve to move toward the seat under the spring bias.
Such systems are eminently satisfactory for use in providing fuel to a fuel rail at a predetermined regulated pressure. It is well recognized that fuel systems with pressure regulators using diaphragms or movable walls have excellent performance characteristics. One of the advantages of the pressure regulator containing a diaphragm or movable wall is that a substantially constant pressure of fuel is supplied to the fuel rail over a full range of fuel flow. Varying pressure in the fuel rail would degrade engine performance. While such pressure regulators have been proven satisfactory, they require a substantial number of diverse parts, complicating assembly and causing increased associated costs. There has thus developed a need in a mechanical fuel system for a pressure regulator without a diaphragm or movable wall which provides the desired engine performance characteristics of substantially constant regulated fuel pressure over a wide range of flow conditions and which is relatively simple and inexpensive to manufacture.